The present invention generally relates to an apparatus and method for the inspection of newly formed hot glass containers for faults. More particularly, the present invention relates to an apparatus and method in which the heat radiation or infrared (IR) self luminance of the hot glass containers is sensed for inspection purposes. Using the apparatus and method of the present invention both dimensional faults and glass distribution faults can be detected thereby allowing removal of any faulty glass containers from a single file stream of containers. Furthermore, by analysing trends for the performance of each of a plurality of hot glass moulding cavities employed in a bottle forming machine it is possible to warn of incipient faults developing in any one of the cavities.
After formation in a bottle forming machine glass containers are transported in single file on a conveyor to an annealing lehr. Within the bottle forming machine there may be several glass shaping cavities, each of which shape globules of molten glass into their final form. The length of a bottle forming production line is generally such that many faulty glass containers may be made within a particular glass shaping cavity before the first of these glass containers exits the annealing lehr. Therefore, it is desirable to be able to identify a faulty glass shaping cavity as quickly as possible, so as to avoid the production of large numbers of faulty glass containers.
GB 1523366 discloses an apparatus and method for the inspection of newly formed glass containers as they proceed from a bottle forming machine towards an annealing lehr. The apparatus comprises two pairs of heat radiation sensors which are located opposite the path of travel of the glass containers between the bottle forming machine and the annealing lehr. These sensors generate individual signals in response to the heat radiation from a glass container and if the signals do not occur in a predetermined pattern the glass container is rejected as being defective.
The apparatus and method of GB 1523366 enable glass containers to be rejected which are grossly mis-shaped or which have fallen over on the conveyor or which have stuck to an adjacent glass container. However, small faults in the glass containers, and particularly solid inclusions in the side walls of the glass containers, may go unnoticed. More especially it is not possible to determine when faults in the glass containers are caused by incipient faults developing within a particular glass shaping cavity in the bottle forming machine.
It is an object of the present invention to provide an apparatus and method for the inspection of newly formed glass containers which will detect dimensional and glass distribution faults.
It is yet another object of the present invention to provide an apparatus and method for the inspection of newly formed glass containers which analyses the performance trend of each glass shaping cavity and which is thereby able to warn of any incipient faults developing within a cavity.
According to a first aspect of the present invention there is provided an apparatus for the inspection of hot glass containers comprising an inspection zone, a camera sensitive to infrared radiation located opposite the path of travel of the hot glass containers through the inspection zone and electronic means for dividing the image of each hot glass container captured by the infrared camera into regions and for comparing data obtained for each region with predetermined parameters to determine whether or not the glass container is defective.
According to a second aspect of the present invention there is provided a method for the inspection of hot glass containers wherein the hot glass containers are viewed by an infrared sensitive camera as they move through an inspection zone, the image of each hot glass container captured by the infrared camera is divided into a plurality of regions and data from each region is compared with predetermined parameters to determine whether or not the glass container is defective.
Within each region two measurement tools are used, namely "calliper" and "window". The calliper measurements determine the distance between distinct edges of the hot glass container or between one edge and another calliper serving as a reference. The window measurements determine both the relative brightness and the grey scale variance of the hot glass container.
In a preferred embodiment of the present invention a "teach" mode is provided in which the image viewed by the infrared camera is initially inspected by an operative who passes or rejects the glass containers according to whether they appear to be acceptable. Certain "taught" parameters of the acceptable glass containers are stored to provide the predetermined parameters with which further glass containers are compared and any that deviate from these stored predetermined parameters are rejected as being defective. Conveniently, the "taught" parameters are stored on a per-cavity basis and only containers from that cavity are compared with these parameters during inspection.
Preferably, the output of the bottle forming machine is synchronised with the inspection apparatus so that the performance of each glass shaping cavity can be monitored and a warning given of any incipient faults developing within a particular cavity. Conveniently, this is achieved by dividing the bottle forming machine cycle (one cycle is defined as the period taken for all the glass shaping cavities to form a bottle) into a number of time slots, one for each cavity and then synchronising the inspection apparatus to the cavity sequence. In this way it is possible to know from which cavity a bottle has come as it passes before the infrared camera.
As stated the camera image is formed by sensing the IR radiation emitted by the hot glass container. The brightness of the camera image is therefore a function of the amount of IR radiation emitted by the container in view, which in turn is a function of the temperature and amount of glass in the field of view. The use of IR self-luminance means that no additional artificial lighting is required. Furthermore, it can be used to sense coloured or opaque glass with the same degree of image quality as flint (clear) glass.
An important part of the apparatus and method of the present invention is, therefore, its ability to sense and inspect hot glass containers without the use of additional or artificial illumination, for clear, coloured and opaque glass.